Alzheimer's disease typically develops slowly and gradually gets worse over the course of several years. It eventually affects most areas of your brain, including those important in memory, thinking, judgment, language, problem-solving, personality and movement.

There are five stages associated with Alzheimer's disease: preclinical Alzheimer's disease, mild cognitive impairment, mild dementia due to Alzheimer's, moderate dementia due to Alzheimer's and severe dementia due to Alzheimer's. Dementia describes a group of symptoms affecting intellectual and social abilities severely enough to interfere with daily functioning.

These stages can help you and your family understand what to expect and plan for the future. It's important to realize that Alzheimer's stages are rough guides based on averages and generalizations. The disease is a continuous process. Your experience with Alzheimer's, the symptoms you develop and when they appear may vary.

Alzheimer's disease begins long before any symptoms become apparent. This stage is called preclinical Alzheimer's disease. You won't notice symptoms during this stage, nor will those around you. This stage of Alzheimer's can last for years, possibly even decades.

Although you won't notice any changes, new imaging technologies can now identify deposits of a substance called amyloid beta that have been associated with Alzheimer's disease. The ability to identify these early deposits may be especially important as new treatments are developed for Alzheimer's disease.

People with mild cognitive impairment have mild changes in their memory and thinking ability. These changes aren't significant enough to affect work or relationships yet. People with MCI may have memory lapses when it comes to information that is usually easily remembered, such as conversations, recent events or appointments. People with MCI may also have trouble judging the amount of time needed for a task, or they may have difficulty correctly judging the number or sequence of steps needed to complete a task. The ability to make sound decisions can become harder for people with MCI.

Not everyone with mild cognitive impairment has Alzheimer's disease. In some cases, MCI is due to depression or a temporary medical complication. The same procedures used to identify preclinical Alzheimer's disease can help determine whether MCI is due to Alzheimer's disease or something else.

Alzheimer's disease is often diagnosed in the mild dementia stage, when it becomes clear to family and doctors that a person is having significant trouble with memory and thinking.

In the mild Alzheimer's stage, people may experience:

Memory loss for recent events. Individuals may have an especially hard time remembering newly learned information and repeatedlyask the same question.

Difficulty with problem-solving, complex tasks and sound judgments. Planning a family event or balancing a checkbook may become overwhelming. Many people experience lapses in judgment, such as when making financial decisions.

Changes in personality. People may become subdued or withdrawn — especially in socially challenging situations — or show uncharacteristic irritability or anger. Decreased attention span and reduced motivation to complete tasks also are common.

Getting lost or misplacing belongings. Individuals have increasing trouble finding their way around, even in familiar places. It's also common to lose or misplace things, including valuable items.

During the moderate stage of Alzheimer's, people grow more confused and forgetful and begin to need help with daily activities and self-care.

People with moderate Alzheimer's disease may:

Show increasingly poor judgment and deepening confusion. Individuals lose track of where they are, the day of the week or the season. They often lose the ability to recognize their own belongings and may inadvertently take things that don't belong to them.

They may confuse family members or close friends with one another, or mistake strangers for family. They often wander, possibly in search of surroundings that feel more familiar and "right." These difficulties make it unsafe to leave those in the moderate Alzheimer's stage on their own.

Experience even greater memory loss. People may forget details of their personal history, such as their address or phone number, or where they attended school. They repeat favorite stories or make up stories to fill gaps in memory.

Need help with some daily activities. Assistance may be required with choosing proper clothing for the occasion or the weather and with bathing, grooming, using the bathroom and other self-care. Some individuals occasionally lose control of their urine or bowel movements.

Undergo significant changes in personality and behavior. It's not unusual for people with moderate Alzheimer's to develop unfounded suspicions — for example, to become convinced that friends, family or professional caregivers are stealing from them or that a spouse is having an affair. Others may see or hear things that aren't really there. Individuals often grow restless or agitated, especially late in the day. People may have outbursts of aggressive physical behavior.

In the severe (late) stage of Alzheimer's, mental function continues to decline and the disease has a growing impact on movement and physical capabilities.

In severe Alzheimer's, people generally:

Lose the ability to communicate coherently. An individual can no longer converse or speak coherently, although he or she may occasionally say words or phrases.

Require daily assistance with personal care. This includes total assistance with eating, dressing, using the bathroom and all other daily self-care tasks.

Experience a decline in physical abilities. A person may become unable to walk without assistance, then unable to sit or hold up his or her head without support. Muscles may become rigid and reflexes abnormal. Eventually, a person loses the ability to swallow and to control bladder and bowel functions.

The rate of progression for Alzheimer's disease varies widely. On average, people with Alzheimer's disease live eight to 10 years after diagnosis, but some survive as long as 25 years. Pneumonia is a common cause of death because impaired swallowing allows food or beverages to enter the lungs, where an infection can begin. Other common causes of death include complications from urinary tract infections and falls.

Albert MS, et al. The diagnosis of mild cognitive impairment due to Alzheimer's disease: Recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. Alzheimer's & Dementia: The Journal of the Alzheimer's Association. 2011;7:270.

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